Dissemination of pathogenic bacteria in tropical hydrosystems: transport and fate of Escherichia coli in the Mekong watershed in Lao PDR

Paty Nakhle, PhD student within M-TROPICS CZO, defended her PhD thesis today at GET.

Fecal contamination of surface water remains a major threat to public health especially in the rural areas of developing countries. Over 70 million people depend on unimproved water resources in the lower Mekong basin. Diarrheal diseases are a leading cause of death especially among children under age five, due to inadequate sanitation infrastructure, low access to safe water resources, and poor medical care in developing countries. Reducing the disease burden requires a better understanding of fecal pathogens dynamics in a tropical context, under the impact of a rapid global change. In this thesis based on a multi-disciplinary approach (in situ monitoring, experimental, statistical and modelling approaches), Paty aimed at identifying the key factors controlling the fate and transport of the fecal indicator bacteria, Escherichia coli (E. coli), at different spatial and temporal scales of the major Mekong tributaries in Lao PDR. Her results reported seasonal variabilities of in-stream E. coli concentrations, and pointed out the importance of land use management as one of major factors affecting E. coli dissemination at watershed-scale in a tropical context prone to soil erosion. Paty underlined the important role of total suspended sediments in providing attached E. coli protection from environmental stressors, and the transport within the watershed. At last, given the importance of the hydro-sedimentary dynamics on bacterial dissemination, Paty assessed the impact of a hydropower dam on the hydrology and water quality downstream of the dam. Overall, her thesis work provides new insights on fecal pathogen dynamics in a tropical context that could be helpful in establishing effective strategies for water resource management.

Congratulations Paty!